# Task ID: 73

**Title:** Implement In-Memory CacheProvider

**Status:** done

**Dependencies:** 71 ✓

**Priority:** high

**Description:** Create the CacheProvider implementation that stages use for caching expensive computations. Start with in-memory cache for Phase 1, with content-addressed keys.

**Details:**

Create `src/mcplocal/src/proxymodel/cache-provider.ts`:

```typescript
import { createHash } from 'crypto';
import type { CacheProvider } from './types';

export class InMemoryCacheProvider implements CacheProvider {
  private cache = new Map<string, { value: string; timestamp: number }>();
  private maxSize: number;
  private ttlMs: number;

  constructor(options: { maxSize?: number; ttlMs?: number } = {}) {
    this.maxSize = options.maxSize ?? 1000;
    this.ttlMs = options.ttlMs ?? 3600000; // 1 hour default
  }

  hash(content: string): string {
    return createHash('sha256').update(content).digest('hex').slice(0, 16);
  }

  async get(key: string): Promise<string | null> {
    const entry = this.cache.get(key);
    if (!entry) return null;
    if (Date.now() - entry.timestamp > this.ttlMs) {
      this.cache.delete(key);
      return null;
    }
    return entry.value;
  }

  async set(key: string, value: string): Promise<void> {
    if (this.cache.size >= this.maxSize) this.evictOldest();
    this.cache.set(key, { value, timestamp: Date.now() });
  }

  async getOrCompute(key: string, compute: () => Promise<string>): Promise<string> {
    const cached = await this.get(key);
    if (cached !== null) return cached;
    const value = await compute();
    await this.set(key, value);
    return value;
  }

  private evictOldest(): void {
    const oldest = [...this.cache.entries()].sort((a, b) => a[1].timestamp - b[1].timestamp)[0];
    if (oldest) this.cache.delete(oldest[0]);
  }
}
```

**Test Strategy:**

Unit tests for: hash() produces consistent output, get() returns null for missing keys, set()/get() round-trip works, TTL expiration works, LRU eviction triggers at maxSize, getOrCompute() caches and returns cached values.